Ocean Drilling Program Explores Large Gas Hydrate Field Offshore Oregon

September 2002

The international Ocean Drilling Program (ODP) just completed a two-month
expedition that investigated the origin and distribution of gas hydrates.
Their findings could help identify locations and quantify amounts of this
potential resource. Gas hydrates are frozen deposits of natural gas that
scientific evidence suggests may eventually serve as a major new worldwide
energy source. Hydrates also have the potential to cause global warming if
released suddenly by landslides because methane is a powerful greenhouse
gas. Although scientists know that gas hydrates are common in the seafloor
on the margins of continents around the world, they do not know how much
hydrate is present.

Scientists onboard the research vessel JOIDES Resolution spent the past two
months during ODP Leg 204 (6 July2 September) studying gas hydrates
offshore Oregon in an area known as Hydrate Ridge. Their primary objective
was to determine how much gas hydrate is present beneath the seafloor in a
region where hydrates have previously been observed and where geophysical
evidence indicates that they are widespread. Dr. Anne Tréhu of Oregon State
University (USA), a co-chief scientist on the cruise, stated, "Measurements
made during this cruise will permit us to update estimates of the volume and
flux of methane and other hydrocarbon gases trapped in the sediments on the
Oregon continental margin and, by extension, in other regions."

Ocean drilling plays a critical role in addressing questions about hydrates
because it provides the only means available to the international academic
community of directly sampling gas hydrates and the sediments that host them
deep beneath the seafloor. In 1995, ODP drilled into gas hydrates off the
U.S. east coast. From that study, scientists have estimated that this area
could contain enough methane to supply US needs for more than 100 years.
They also found evidence suggesting that hydrates are involved in the global
climate cycle and that they can cause massive landslides. The next natural
step for ODP was to study gas hydrates on a geologically active margin. Dr.
Gerhard Bohrmann, GEOMAR (Germany), a co-chief scientist on the cruise,
noted, "The Oregon margin is an excellent place to study the dynamics of
hydrate formation."

Among the most surprising findings of Leg 204 was the rate at which hydrate
is forming near the summit. Salts are excluded when hydrates form, and the
excess salt in the pore water diffuses away from the gas hydrate with time.
However, if the hydrate forms very rapidly, the salts do not have time to
diffuse and the water in the sediment pore space will become saltier than
seawater. Dr. Marta Torres of Oregon State University and acting ODP
postcruise staff scientist, explained, "During Leg 204, high concentrations
of sea salts were observed in the upper 10-15 meters of sediment at the
summit, indicating that hydrate is forming very rapidly below the seafloor
in this region."

Scientists also gained an understanding of the importance of sediment
properties (composition and size of grains) in the distribution of hydrate
within the sediments, which may provide clues to their locations. Says
Bohrmann, "Coarse-grained layers are the primary conduits for fluid flow and
tend to have the highest concentration of hydrate."

During Leg 204, scientists used the floating laboratories of the JOIDES
Resolution to conduct chemical and physical studies on core samples. Leg
204 was also a test-bed for several technological innovations that promise
to make an important contribution to hydrate studies in the future.
Breaking new ground, Leg 204 saw, for the first time, laboratory
measurements of the physical properties of natural hydrates at subseafloor
pressures without ever releasing this pressure. This was made possible by
new tools developed by the European HYACINTH consortium. It also saw the
first simultaneous acquisition of both core samples and
Logging-While-Drilling data using tools developed in a US-based
industry/academic collaboration. In an example of successful technology
transfer, infrared thermal imaging cameras developed for other uses proved
invaluable for rapidly identifying hydrate samples buried in cores. The
thermal imaging cameras, pressure vessels to preserve key hydrate samples
for further study, and other and logging and physical properties measurement
equipment and equipment upgrades were supplied by the U.S. Department of
Energy's National Energy Technology Laboratory. Frank Rack, Joint
Oceanographic Institutions (USA) and acting ODP staff scientist on the leg,
stated, "Leg 204 was the first of what we hope will be a series of drilling
expeditions dedicated to understanding the distribution, concentration and
environmental impact of gas hydrates in nature."

Scientists on Leg 204 represented the United States, Germany, Japan, Canada,
Spain, Norway, the United Kingdom, Taiwan, the People's Republic of China,
and South Korea. After the cruise, these scientists will return home to
continue study on the cores. Tréhu stated, "Analysis of this extensive,
integrated data set is just beginning. Ultimately it will yield a better
understanding of the processes that form and focus hydrate in nature and
lead to more precise methods to predict regional hydrate distribution and
concentration."

ODP is an international partnership of scientists and research institutions
organized to study the evolution and structure of the Earth. While ODP is
funded primarily by the US National Science Foundation and its international
partners, the US Department of Energy and the European Commission played
important roles in funding much of the innovative technology used on this
Leg. The Joint Oceanographic Institutions manages the program. Texas A & M
University is responsible for science operations, and Lamont-Doherty Earth
Observatory of Columbia University is responsible for logging services.